GregSY "Why the hole in the stock?"

That would be for a breeching rope, a common feature of shoulder guns that would also be fired from a stanchion or a punt (in the latter case the rope might lead through the stemblock of the boat). Basically it just helped with recoil.

As to recoil in a common or garden eight as opposed to something with the weight of a harpoon as payload, it's modest enough.

regards
Eug